A parking lot next to Wrigley Field is expected to be the site this winter of a public ice-skating rink starting Dec. 15, Chicago Park District officials said today.  The park district board was set to vote this afternoon on a permit agreement with the Cubs that would allow the rink to be built. It would be run by Westrec, the same firm that operates other city rinks, according to the park district.  The rink will be constructed by Arena Systems, St. Paul, MN.  The rink, which would be open to the public from Dec. 15 to Feb. 28, would be located at Addison and Clark, and called "The Rink at Wrigley."  The estimated cost of the rink is $300,000, split evenly between Westrec, the park district and private donors.  The Cubs are among the private donors whose contributions will make up that $100,000 piece, along with several other entities, including the Blackhawks, McDonalds Corp. and other local businesses, said Mike Lufrano, a spokesman for the club.